Updated WebStatePolicyDecider::ShouldAllowResponse comments.

Removed references to unsupported iOS 9.

Bug: None
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: I1cea95523f85ee82b614a959eab5fc5c7bc01ea0
Reviewed-on: https://chromium-review.googlesource.com/1217353Reviewed-by: Mohammad Refaat <mrefaat@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590056}

ios/web/public/web_state/web_state_policy_decider.h

@@ -60,8 +60,8 @@ class WebStatePolicyDecider {
   // Never called in the following cases:
   //  - same-document navigations (unless ititiated via LoadURLWithParams)
   //  - CRWNativeContent navigations
-  //  - going back after form submission navigation (except iOS 9)
-  //  - user-initiated POST navigation on iOS 9 and 10
+  //  - going back after form submission navigation
+  //  - user-initiated POST navigation on iOS 10
   virtual bool ShouldAllowResponse(NSURLResponse* response,
                                    bool for_main_frame);